In this quarter of a century, a body fluid purifying technology by an extracorporeal circulation, especially a blood purifying technology, has accomplished a remarkable progress.
Above all, hemodialysis has been widespread as a blood purifying method that executes a kidney function of a renal insufficient patient. A principle of this hemodialysis lies in that blood and dialysate are contacted with each other through a dialysis membrane and body wastes in blood are discharged to dialysate by a difference in concentration of solute between both liquids. Various hemodialyzers which use a plate-type or hollow fiber-type membrane, etc. have been developed and used clinically.
Hemofiltration or hemodiafiltration are also used as a blood purification method that uses a membrane as in hemodialysis.
On the other hand, various blood purification methods that use adsorbents are examined, and, an adsorber which is used to assist a kidney function and charged with a granular active carbon is on the market.
In recent years, in a field of hemodialysis, it becomes an issue that small molecular weight proteins accumulate in blood of a renal insufficient patient who undergo a hemodialysis therapy. It is generally thought that this accumulation occurs because these small molecular weight proteins, which should be metabolized with a kidney in a normal state, cannot be removed by a conventional hemodialyzer.
As an example of such small molecular weight proteins, β2-microglobulin is given, which is a protein constituting an amyloid deposition of a dialysis-related amyloidosis patient as revealed in 1985 by Gejyo et al. The molecular weight of β2-microglobulin is reported to be 11,731 (F. Gejyo et al., Biochemical and Biophysical Research Communications, Vol. 129, No. 3, Pages 701-706, 1985).
In order to improve the performance of removing such a small molecular weight protein, a means of enlarging the pore size of hemodialysis membrane is used, and a hemodialyzer using the so-called high performance membrane has been developed and used clinically, but, at present, it is hard to say that enough removing performance is accomplished.
Also it becomes possible to remove these small molecular weight proteins in a considerably high efficiency by a hemofiltration method or a hemodiafiltration method, but problems lie in points that these methods need quite a large quantity of fluid replacement which a usual hemodialysis does not need and that an additional equipment is necessary to a dialysis control machine used widely.
Further, in methods using these membranes, it becomes an anxious issue that there occurs pollution by toxic substances such as an endotoxin of a bacterium, etc. from the dialysate side, which accompanies enlarged pore size of membranes.
On the other hand, the adsorber which is charged with a granular active carbon is not originally designed for adsorption of proteins, and is poor in adsorbing ability for small molecular weight proteins, and it is the present situation of the adsorber that a sufficient removal of these proteins cannot be performed.
On the other hand, an immunocompetent cell produces various kinds of active substances when causing immune response. A part thereof is a proteinaceous substance called cytokine and plays a greatly important role as a biophylactic factor which is closely related to various kinds of antigen-specific or non-specific inflammatory responses. Essentially, cytokine is necessary and indispensable for maintaining biological homeostasis and is produced excessively in pathological conditions such as inflammation and the like, relating to the formation and prolongation of inflammation and the like.
Among the cytokines, especially, ones having chemotaxis are generically named chemokines. Chemotaxis is also referred to as chemotropism, and means tropism caused by difference in concentration of a chemical entity. It is known that the substances referred to as chemokines form one family for their structural characteristics.
Chemokines are characterized in that they exist mainly as proteins having a molecular weight of from about 6,000 to about 10,000. Depending on the kind of chemokines, however, there exist chemokines which form dimers or tetramers in fluid, and chemokines having a molecular weight more than 10,000 because of O-glycosylation. Also, chemokines are classified into the following two subfamilies according to their structural characteristics. One is CXC subfamily, and the other is CC subfamily. As shown in a Review of M. Baggiolini et al, “CC CHEMOKINES IN ALLERGIC INFLAMMATION”, Immunology Today, 15, 127, 1994, a chemokine has four cysteine residues (hereinafter a cysteine residue is referred to as C) in a position firmly conserved in its molecule. When such four Cs are referred to as C1, C2, C3 and C4 in that order from N-terminus, CXC subfamily is that wherein one optional amino acid (hereinafter referred to as X) exists between C1 and C2, and CC subfamily is that wherein no amino acid exists between C1 and C2. Further, it is shown that chemokines in each subfamily have homology in a sequence of amino acids other than Cs (e.g., Chihara's report, Clinical Immunology, 27 [Suppl. 16], 162-171, 1995).
It has been thought that CXC subfamily acts mainly on a neutrophil among leukocytes, while CC subfamily acts mainly on a monocyte, an eosinophil, a basophil and a lymphocyte among leukocytes. Recently, however, it has been suggested that they exert their effects on various kinds of cells. For instance, it is known that interleukin-8 shows physiological activities on a lymphocyte, a basophil, an eosinophil, an epidermal keratinocyte, a melanomatous cell, a fibroblast and an endothelial cell as well as a neutrophil, although interleukin-8 is an interleukin having chemotaxis among interleukins and is a chemokine belonging to CXC subfamily (Matsushima, Clinical Immunology, 27 [Suppl. 16], 147-154, 1995).
Further, it is known that, for instance, on a human monocyte, there exist not only receptors specific to each of monocyte chemoattractant protein-1 (hereinafter referred to as MCP-1) and macrophage inflammatory protein-1 (hereinafter referred to as MIP-1) which are chemokines belonging to CC subfamily, but also a common receptor specific to three kinds of chemokines belonging to CC subfamily, i.e., MCP-1, MIP-1 and RANTES (Regulated upon Activation in Normal T cells Expressed and Secreted) (Matsushima, Clinical Immunology, 27 [Suppl. 16], 147-154, 1995). This finding suggests that there exist chemokines in one subfamily which exert the same physiological activity through the same receptor.
Once a living body has stress or infection from the outside, inflammation is caused as a biophylactic response, and there arises infiltration of leukocytes into an inflammatory site. Such infiltration of leukocytes into an inflammatory site is caused by leukocyte chemotactic factor produced at the inflammatory site. It is known that a chemokine plays a role as a causative factor of the infiltration of leukocytes. In fact, it has been demonstrated that in an acute inflammation model in rabbit, administration of an antibody against interleukin-8 (anti-IL-8-antibody) being one of chemokines blocks infiltration of neutrophilics at a inflammatory site and inhibits a disorder of organ accompanying acute inflammation (Sekido et al., Nature, 365, 654-657, 1993).
Furthermore, recently it has been reported that a network of cytokines is activated by overproduction of various cytokines, and the induction and activation of neutrophils are caused by overproduction of chemokines due to the activation of the network of cytokines, in pathological conditions included in a conception of systemic inflammatory response syndrome (SIRS) (Endo et al., Intensive & Critical Care Medicine, 4, 1357-1365, 1992). It is suggested that these progress systemic inflammatory response, and shock, a tissue disorder and pluriorganic insufficiency are caused, and then death may come.
It is suggested that at a pathologic site with allergic inflammation, various inflammatory cells such as a lymphocyte and an eosinophil infiltrate by action of chemokines such as RANTES, platelet factor-4 (hereinafter referred to as PF-4) and macrophage inflammatory protein-1α (hereinafter referred to as MIP-1α), as key substances.
Also, for instance, in case of carrying out blood extracorporeal circulation such as dialysis therapy, the possibility has been suggested that chemokines are overproduced by stimulation to an immunocompetent cell by means of contact with an artificial material, irritants of which typical example is microbial endotoxin in dialysate, various irritant factors existing in blood or tissue, and the like. For instance, in dialysis amyloidosis or carpal tunnel syndrome which is a complication accompanying a long-term dialysis therapy, the possibility has been suggested that MCP-1 or MIP-1α is overproduced and relates to formation of pathological conditions (Inoue et al., Nephrology Dialysis Transplantation, 10, 2077-2082, 1995).
Further, an abnormally high concentration of interleukin-8 being one of chemokines has been detected at an inflammatory site or in peripheral blood of patients with diseases such as gouty arthritis, psoriasis, contact dermatitis, idiopathic fibroid lung, adult respiratory distress syndrome, inflammatory bowel disease, immune angiitis, urinary tract infection, cardiac infarction, asthma, respiratory tract infection, perinatal infectious disease and rejection in organ transplantation, as compared with a normal human (Menekiyakuri, 12, No. 1, 15-21, 1994).
Also, there abnormally appear interleukin-8, RANTES, MCP-1, MIP-1α and macrophage inflammatory protein-1β (hereinafter referred to as MIP-1β) in rheumatoid arthritis; MCP-1, MIP-1α and MIP-1β in crescentic glomerulonephritis; interleukin-8 and MCP-1 in chronic glomerular nephritis; and MCP-1 in lupus nephritis. It is suggested that the chemokines concern formation of pathological conditions of the above-mentioned diseases.
Until now, there are few reports as to a method for removing such chemokines which have various functions in body fluid. There is disclosed only a method for purifying blood with an adsorbent for removing an endotoxin and/or a cytokine caused by the endotoxin, which comprises a porous carrier having a cationic functional group on the surface (Japanese Unexamined Patent Publication No. 6-312017). However, there is described neither measurement of the cytokine nor adsorption of the cytokine in working examples thereof.
The application of the so-called anti-chemokine therapy is also considered wherein chemokine's action is inhibited by administering an antibody against the chemokine or a substance which inhibits binding of the chemokine to a receptor thereof. However, it is necessary to prepare and administer an antibody against each chemokine in order to inhibit such action by administration of the antibody or the like, because it is suggested that many kinds of chemokines abnormally appear in pathologic conditions accompanied with chronic inflammation such as the above-mentioned rheumatoid arthritis. Further, an antibody or the like to be administered must not exert bad influence upon a human body, and it is considered that development thereof requires long term and a great cost. Therefore, it is hard to say that such therapy is a suitable one.
In view of the problems of prior arts mentioned above, an object of this invention is to provide an adsorbent capable of efficiently removing substances related to malady in body fluid, especially small molecular weight proteins including β2-microglobulin or chemokines, a removing method capable of removing substances related to malady in body fluid, especially small molecular weight proteins including β2-microglobulin or chemokines by using said adsorbent, a device for body fluid purification and a system for body fluid purification.
A particular object of this invention is to provide a device for blood purification and a system for blood purification which are capable of removing efficiently and sufficiently small molecular weight proteins, typically β2-microglobulin or chemokines in blood and which are simple and safe.